hash: Add function to find hash_algo struct with progressive hash

The hash_algo structure has some implementations in which progressive hash
API's are not defined. These are basically the hardware based implementations
of SHA. An API is added to find the algo which has progressive hash API's
defined. This can then be integrated with RSA checksum library which uses
Progressive Hash API's.

Signed-off-by: Ruchika Gupta <ruchika.gupta@freescale.com>
CC: Simon Glass <sjg@chromium.org>
Acked-by: Simon Glass <sjg@chromium.org>